Metallurgical process



April .1, 1924. 1,489,121

, W. E. GREENAWALT METALLURGICAL PROCESS Original Filed May l0 1920 IIV $55 Umwwum IN VENTOR.

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narran site@ VVLLIAVL' E. GREE'NAVVALT, OF DENVER, COLORADO'.

METALLURGICAL PROCESS.

Application filed May 10, 1920, Serial No. 380,361. Tienen/'cd August 27, 1923.

Be it known that ll, lVILLrAM E. Gamm- AwAnr, a citizen of the United States, residingl in the city and county of Denver and State of Colorado, have invented certain new andA useful Improvements in Metallurgical Processes, of which the following is a specification.

My invention relates more particularly to the extraction of copper from its ores by solvent processes. lt has for its more immediate object the'productioncf the metal by the indirect method of chemically precipitating the copper from its solutions and then obtaining the electrolytic metal from the chemical precipitate.

This process may be considered as a continuation in part of that. disclosed in my copending application, Serial No. 15,583, tiled March 19, 1915, and a modification of the processes disclosed in my co-pending vapplications, `Serial No. 228,952, filed April 16, 1918 and Serial No. 239,255, filed June 10, 1918.

Serial No. 15,583, dis/closes the general idea of precipitating copper from its solutions with hydrogen sulphide and applying the copper sulphide precipitate to van electrolyte containing ferrie iron. Serial Numbers 228,952, and 239.255, disclose methods in more or less detail, for practically carrying out the disclosure in Serial No. 15,583.

ln the present application the same general idea. is applied as in the above applications, but in a somewhat different Way. ln this process it is proposed to avoid the hannful effects in the electrolysis incident to electrolyzing foul leach solutions, by maintaining the leach solutions and the electrolyte entirely separate. and taking ad antage of the property of ferrie salts to quickly and eliectively dissolve the copper from the sulphide precipitate, without subjecting the precipitate to any unusual preliminary treatment.

The processes set forth in the above applications will usually be preferred, but when the ore being treated has a very low copper content. and the resulting leach solutions are too lou' in copper and too highly charged with iinliiurities to make electrolysis of the leach solutions advisable, the present process may be satisfactorily applied. rlhis process may with advantage be applied to performed, both the acid and the iron are irrecoverably lost, and the-resulting cement copper is an undesirable end product which has to be smelted and refined in the usual Way,rthe same as a high grade ore or concentrate. In my present process, by taking advantage of the broad disclosure in SerialV No. 15,583, it is possible to carry out the. precipitation automatically, and have as an end product the pure electrolytic metal, While at the saine time regenerating both the leach .solution and the electrolyte. The process may be variously applied, but the preferred method, on complex ores, may be described as follows, reference being made to the accompanying drawing, which represents a flow sheet in diagrammatic section.

rlhe ore, containing copper and assumed to contain gold, silver, and lead, is crushed to a suitable. fineness and charged into the leaching vat. lf the ore is a sulphide, roasting, as a preliminary treatment, will be desirable, and if the orc contains silver and lead in considerable amounts, chloridizing roasting may be necessary. lt is immaterial, so far as the process is concerned, Whether the ore in the leaching vat is percolated or agitated.

lf a chloride solution is used, all the metals may be dissolved from the ore. Gold chloride is readily soluble in Water. Lead and silver chlorides or sulphates are fairly soluble in Warm chloride. solutions. Cupric chloride or sulphate are highly soluble in water, and cuprous chloride is fairly soluble in a. heated chloride solution. Both ferrie and eupric chloride act to chloridize some of the silver remaining unchloridized by the chloridizing roasting.

,The metal solution issuing from the leaching vats flows into the HES precipitator, Where the metals are continuously and completely precipitated with the hydrogen sulphide, with thel simultaneous regeneration of an equivalent of acid, as is Well known. The precipitated and-regenerated acid solution Hows into the separator No. 3, where the sulphide precipitate is separated from the regenerated acid solution. The acid soies lllti ythem tothe ferrie salts' lution is returned to the ore to passthrough.

another cycle. 5

The precipitate, thoroly washed to ,eliniii nate the soluble chlorides if a chloride solu-4 -tion is used as the solvent, is flovvedas a thickened sludge from the separator No. 3 to the agitator No. 1. The solvent for the copper in the precipitate, in theagitator, is preferably a solution of ferric and ferrous sulphate. The gold, silver, and lead sulphides, as precipitated with H25, are

quite-insoluble in a ferrie sulphate solution.' The copper, ofthe precipitated copper sul;

phide, oni'the contrary, is quite readily. dissolved lWith ferric sulphate, especially -in a hot solution. The reaction is The reaction is quite a rapid one with precipitated copper sulphide, and the reduction of the ferrie salts can quickly be made coinplet-e, or practically so. The reduced iron solution-containing the copper in solutions las sulphate,iows into the separator No. 2,

where the sulphide precipitate 'is separatedlfrom the clear overl-lowing;r solution, The

separated precipitate is either returned to agitator No. 1 orpassed on to agitator No. 2, and progressively advanced through the system. The clear reduced copper sulphate solution preferably quite rich in copper flows into electrolyzer No. 1, Where a -portion of the eopper'is electrolytically deposited, with the simultaneous regeneration of the ferric-` sulphate. Under the perfect depolarization conditions of this process the amount of acid regeneratedwill be comparatively small Vthe oxygen liberatedat the anode .will mostly combine withl the ferrous salts to convert The ferrous sulphate acts as an efficient depolarizer. and this tends to materially reduce the E. M. F. in the deposition of the copper, especially if carbon anodes are used. lt is believed that With agitation, a heated electrolyte, and with an elecltrolyte .fairly high in ferrous iron. and a moderate current` density, a practically complete depolarization can be effected so that carbon anodes Will not .show any unusuall disintegration, as disclosed 1nmy Patent.

No. 1,314,742, Sept. 2` 1919. The rate.of

flow through the electrolyzers is preferablv regulated so that the issuingr electrolyte will not contain mbre than 0.25% ferric'iron.

higher ferric iron content may materially reduce the eHicie-no and increase the danger of anode disintegra ion. The electrolyte` is-.

, suing from the electrolyzer No. 1. containing` about 0.25% ferrie iron and deprived of some of' its copper, flows into agitator No. 2. Where more copper is brought into solution by the ferrie sulphate formed in electrolyzer No. 1, and the ferric sulphate isagain reduced t'o the ferrous -condition by reacting Witht'he copper sulphide precipitate in maaier the agitator, The mixture of electroyte and arated; from the 'electrolyte and the .clear overflowingelectrolyte is passed on to electrolyzer No.f2, Where more copper is deposv itedl and more ferric salts regenerated. `Inthis Waythe cycle may be repeated 'as often as desired, and finally, theelectrolyte may be returned to the rst agitator to pass through" another coniplete cycle, as described.`

The impoverished copper precipitate, containing also considerable'sulphur, as shown by the following equation,

is flowed into .the filter press to reduce its moisture. From the filter it is charged into the roasting furnace, Where the, sulphur is 'sulphide precipitate flows into* separator No.2, Where the sulphide precipitate is sep,V

' 2. cusarrezrsoapousogeresogfs,

sesv

burned olf andthe remaining copper largely converte-d into`the sulphate and oxide, and

this roasted material may be applied to the electrolyte to dissolve the copper and reduce the excess acidity, if excess acidity develops. If the -electrolyte becomes too acid. it is applied to the ore. `A vsmall portion of the electrolyte is preferably continuously discarded and applied .to theore, and replaced lwith a fresh iron salt solution.

The ferrous anl ferric sulphate electrolyte isreplenished from the ferrous sulphate formed 'in the ILS generator by the action of sulphuric acid on matte:

3. resafngsorsons.

or ferrous salts, it may at times he dvesirablel to convert some of the ferrous salts into the ferrie condition before applyingr the leach acid solution to the ore. This maybe done in electrolyzer No. 3. Ferrie chloride is an If the ore-'contains zcold the leach lsolution may also be charged with chlorine generated frolnchloridcsin electrolyzer No. 3.

The precipitated gold, silver,- and lead sulphides will gradually,accumulate in the'precipitate` and when the amount is sutlicient, the. precipitate is filtered, and the filtered precipitate eliminated from the circuit` to .be given further treatmentas desired. The

further treatment of this precipitate is not directly related tothe present process.

lt will be seen that this process involves loo 'eflicient chloridizer of both silver and lead.-

titi

the use of two independent solutions, and that the nature of the leach solution, its Jfoulness or its composition, is practically Iindependent of the electrolyte. The electrolyte may be maintained as highly charged with,

'worth recovering, it will usually be found advisable to leach with a sulphate rather than with a chloride solution. The nature of the leach solutionis more or less immaterial in the general ope-ration of the process. Other solutions, such as hyposulphite, may at times be possibly used to advantage.

'llhe process, vin its application to `copper leaching, oli'ers marked advantages over iron precipitation. Hydrogen sulphide precipitation of copper from its leach solutions, has

never come into general use, notwithstand= ing many of its evident advantages, and this is largely due to the voluminous nature of the precipitate and the difficulty and expense encountered in filtering, drying,

smelting, and refining of this precipitate.Y

The characteristic which is so undesirable in the fusion refining of .the precipitate, is, however highly advantageous in my process, for the evident reason that the voluminous nature of the precipitate offers a large ex- 4. CuClg-l-CuSzQCuCl-l-S.

This cuprous chloride is readily converted into the cuprous sulphide, by the action of rllhe HC1 is easily removed by Washing, so that the pure C1125 remains, free from chlorides, and this CugS, is then used as a reducing agent, to eliminate more chlorine:

6. 'UuClg-l-CugSzOCuCl-l-CuS.

llt will be seen therefore that in the ordinary operation of the process the chlorine may be automatically and eectually eliminated from the electrolyte.

Chlorine, in the electrolyte, has a very deleterious eiiect on lead anodes` as also anodes composed of, ferrosilicon: it is, however, Without action on carbon anodes, and carbon anod'es may ordinarily be used :in the operation of this lprocess dueto the very effective depolarization obtainable by the high iron electrolyte, as described.

lt fret uently happens that the orc or the leach solution contains considerable chlorine, and much of the copper is dissolved as the cupric chloride. In such cases I prefer to tirst apply sulphur dioxide to all, or a portion, of the leach solutions preparatory to hydrogen sulphide precipitation, and thus precipitate a large portion ofthe copper as `the insoluble cuprous chloride. Sulphur dioxide precipitation is cheaper than hydrogen sulphide precipitation and regencrates more acid. On the other hand the lcopper precipitated with sulphur dioxide 1s 1n the more or less undesirable form ot cuprous chloride, which does not readily lend itself to' electrolysis. It is desirable to convert the copper in the cuprouschloride into some other combination. This is conveniently done by adding calcium hydroxide (quick lime) to the precipitated cuprous chloride, which converts the copper into the form of cuprous oxide, with the formation of calcium chloride. The cuprous oxide is then separated from the very soluble calcium chloride, land Washed, which leaves practically the pure cuprous oxide. rlhis cuprous oxide is then applied to the electrolyte to regulate its acidity, and to convert the oxide into the electrolytic copp llt this step in the process is advisable, all, or a portion, of the leach solution containing'cupric chloride is iowed from the leaching vat into the SO2 precipitator, Where the soluble cupric chloride is converted into the insoluble cuprouschloride. The precipitate and solution low into the separator No. It, Where the precipitate is separated4 from the solution. The solution, still containing some copper, is flowed into the H2S precipitator, and passes through `the circuit, as already described.

rlhe cuprous chloride precipitate is flowed into the agitator No. 3, Where the calcium hydroxide .is added and the mixture agi` tated. The calcium hydroxide reacts withl the cuprous chloride to form cuprous oxide and calcium chloride. The mixture of solution and precipitate flows into-the separator No. 5, Where the calcium chloride is separated -from the cuprous oxide precipitate. The cuprous oxide is thoroughly Washed to free it from. chlorides, and is then applied to the electrolyte, by flowing it into separator No. 2 and through the reducing system, as desired, to react with the excess acid formed by the electrolysis, and to convert the oxide into the electrolytic metai. ln this way, all the copper may be converted into the electrolytic metal, While the electrolyte may be controlled both as to its acidity and its `terric iron content. The rate of. dow

ino

through the electrolytic systemwould ,also be a governing and regulating factor. j

It is desirable to Work with a fairly Warm electrolyte, say, at 125 deg. F'. .It is .also

desirable to agitatethe electrolyte. Heating and agitating the electrolyte reduces'the E. M. F. required for the deposition of the ing the sulphide precipitate fromthe leach solutions, treating the sulphide precipitate with a ferrie sulphate solutiontore-dissolve the copper of the precipit atewith the simultaneous reduction of the ferrie sulphate 4to the ferrous sulphate, and electrolyzing the resulting copper sulphate solution containing ferrous sulphate to obtain thejelectrof lytic metal and regeneratel ferrie sulphate-,to

dissolve more copper from the sulphide-precipitate.

2. A metallurgical process, comprising treating ores of metals With a solvent for the metals, precipitating the metals out of the leach solutions as thesulphides, separat-v ing the sulphide precipitateffrom' the .leach solutions, treating the sulphide precipitatev with a ferric salt solution tore-dissolve t-he f metals soluble in a ferricl salt solution with 40 the simultaneous reduction of the ferrie salt to the ferrous salt, and electrolyzing theresulting metal salt solution to deposit the metal and regenerate the ferrie salt' with which tovdissolve more metal rom the sull-l phide precipitate.

3.; A metallurgical `process comprising treating ores of copperwith' a solvent'for the copper, recipit'ating the copper ou t of` the leach so ution as the sulphide, separat,

ing the sulphide precipitatefrom the leach solution, returning the leach solution to the ore, treating` the sulphide precipitate with a ferrie salt solution' distinct from the-leach' solution to re-dissolve the copper With the n simultaneous reductionior` the erric salt'to the ferrous salt, and electrolyzing the result.-

comprising' applying a chloride solution to ing copper solution to deposit the metal and regenerate the ferrie salt Witli which to dis-,y so

ve more ycopper from the sulphide precipitate. r .LLA metallurgical process comprising treating ores of metals with a solvent for the metals, chemically vprecipitating the metalsout of the. leach solutions, separating 6 5 the chemical precipitate from the leach solutions, treating thechemical precipitate with a-solution distinct fro'mfthel leach solutions to re'-dissolve*the metals, and electrolyzing the resultingl metal solutions With insoluble anodes -to electrolytically deposit the metals f and regenerate the solvent for the chemical precipitate. v 5. A metallurgical process comprising treating ores of metals -with a solvent for the metals,. chemically precipitating 'the metals out of the leach solutions, separating the chemical precipitate from the precipitated leach solutions, returning the precipitated leach solutions to the ore, treating, thef chemical precipitate with a solution distinct ro'm theleach solutions .to re-dissolve the metals', and electrolyzing the resulting metal solution with insoluble anodes to electrolytically deposit the metals and vregenerate the solvent for the chemical precipitate.

6. A process comprising precipitating copper from its solutions With hydrogen sul.- phidegenerated' from ferrous sulphide and sulphuric acid, electrolyzing the resulting ferrous sulphate solutions to convert the ferrous salt into the ferrie salt, treating the copper sulphide precipitate with the ferrie 'salt solution so formed, and electrolyzing the resulting copper sulphate solution containing ferrous sulphate to deposit the copper c and regenerate ferrie sulphateA with which to dissolve more copper from the sul-4 phide precipitata I 7. A process comprising precipitating copper from its solutions with hydrogen sul phide generated from sul'phuric acid andferro'us sulphide, treating the resultingcopper sulphide. precipitate with av solution of 'a ferrie Lsalt as. an electrolyte, and adding l the iron salt solution resulting from the generationfof the hydrogen sulphide to the electrolyte.A

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8. A'process oftreatingores of metals ,comprising applying fa chloride solution4 to an ore containmg copper andother metals, applying a sulphide 'precipitant to the rethe metals, separating the resulting sulphide vprecipitate from the'solution, applying the sulting metal chloride solution to precipitate i 9. A process of treating ores of metals precipitate' from the solution, treating the' preci itate with a ferrie sulphate solution to disso ve the copper, electrolyzingthe resulting copper solution containing salts 'of iron -ing precipitate from the precipitated chloride solution, returning the chloride solution to the ore, treating the chemical precipitate with a ferrie sulphate solution to dissolve the copper, electrolyzing the resulting copp r sulphate solution containing salts oit iron to deposit the copper and regenerate. the ferrie sulphate to dissolve more copper from the chemical precipitate, and from time to time recovering the metals other than copper from th'e sulphide residue.

11A process comprising precipitating copper from its solutions with hydrogen` sulphide generated by reacting'on ferrous sulphide with sulphuric acid and applying the resulting iron sulphate solution to the copper sulphide precipitate as an electrolyte.

12.17A process comprising precipitating copper 'from its solutions as the sulphide, applying the sulphide precipitate to an elec trolyte containing salts of iron and small quantities of chlorine whereby the soluble cupric chloride is converted into the insoluble cuprous chloride, and separating the insoluble cuprous chloride from the electrolyte.

13. A' process comprising precipitating copper from its solutions as the sulphide, applying the sulphide precipitate to an electrolyte containing salts of iron and small quantities of chlorine to convert the soluble cupric chloride into the insoluble cuprous chloride, separating the insoluble cuprous chloride from the electrolyte, applying hydrogen sulphide to the cuprous chloride to convert the cuprous chloride into the sulphide,I and applying the resulting sulphide to the electrolyte as a reducing agent.

14. il process ,comprising precipitating copper from its solutions as the sulphide',

applying the sulphide precipitate to an electrolytecontaining salts of iron and small quantities lof chlorine to dissolve the copper from the precipitate and convert the ferrie salts into the ferrous salts and the cupric chloride into the cuprous chloride, separat-l ing the insoluble cuprous chloride from the electrolyte,l applying a reagent to the cuprous chloride capable ot converting the chloride into the-sulphide, and applying the resulting sulphide to the electrolyte.

l5. .A process coi'nprising treating ores ol copper 'with an acid solvent for the'cop per, applying hydrogen sulphide tothe resulting copper solution to precipitatev the copper, separating the sulphide precipitate from the regenerated acid solutionreturn ing the regenerated acid solution to the ore, treating the sulphide precipitate with a. ferric salt solution to ire-dissolve the copper with the simultaneous reduction of `the ferric-salt to theferrous salt, and electrolyzing the resulting copper solution to deposit the metal and regenerate the'ferric salt with which to dissolve more copper from the sulphide precipitate 16.' A metallurgical process comprising treating ores of copper with a solutionlcontaining chlorine, applying sulphur dioxide to the solution to precipitate a portion of the copperas the cuprous chlorine, separating the solution from the precipitate and then applying hydrogen sulphideto the solution to precipitate the remaining copper as the sulphide, separating the solution from thel sulphide precipitate and returning the solu-` tion to the ore, applying the sulphide pre cipitate to yan electrolyte capable of being regenerated by ithe electrolytic deposition' of the copper, converting the cuprous chloride obtained from the sulphur dioxide precipitation into the cuprous oxide, and applying i the cuprous oxide precipitate to the electrolyte.`

17. A metallurgical process comprising treating ores of copper Witha solution con taining chlorine, applying a reducing gas to the leach solution to chemically precipitate the copper, separating the resulting chemical precipitate from the leach solution and returning the leach solution to the ore, applying the chemical precipitate to an electrolyte separate and distinct from the leach lsolution which is capable of dissolving the copper fromthe precipitate and or beingk regenerated by electrolysis, and then electrolyzing the resulting copper ysolution to deposit the copper and lregenerate for the chemical precipitate.

18; 'A metallurgical process comprising treating-ores of copper with a solution for the copper, precipitating the copper from` the resulting solution as a chemical compound, separating the resulting precipitate from the precipitated solution and returning the 4solution to the ore, applying the chemical compound precipitate to an electrolyte separate and distinct from the leach solution Whichisk capable oit re-dissolving the copper and of being regeneratedby electrol ysis, and'electrolyzing the resulting copper solution' to Ideposit the copper and regenerate the solvent for the copper in the chemical compound precipitate.

19. A. metallurgical process comprising treating ores of copper with a solution containing chloride, precipitating part of the copper from the chloride solution as cu- Aprous'chlmide and part as the sulphide, con verting the copper in the chloride precipilll@ tate into the oxide, applying both the sulphide and 'oxide precipitateto an elect-rof klyte separate and distinct from the leach so lution, and electrolyzing the resulting cop'-v per solution to obtaincthe electrolytic metal.

20. A' metallurgical process comprising treating ores of ,copper with a chloride soglution to dissolve the copper, applying sul- Jeleetrolyzing 'the resulting :copper solution phur dioxide to the resulting copper solu-` tion to precipitate a portion of the copper as the cuprous chloride, converting the copper in the cupr'ous chloride :into a chemical combination free from chlorine, applying the resulting copper compound toa .solution capable of dissolving the copper and capable ot- 'being regenerated `by electrolysis, and

. to obtain the electrolytic metal and regenerizo 1,

ate thesolventfor the copper.

21.-A metallurgical process comprising' treating ores otcopper with a-solvent for the copper, precipitating thefcopper fromY the resulting solution as thecuprous chloride," converting the copper in the cuprou's chloride into the oxide,'and then .electrolyzing the resulting o'Xide'to obtainlthe electrolytic metal.

- 22. Ajmetallurgical processA comprising ,treating ores of copper withv a. solvent for. the copper, A'precipitating the copper from'. .the resulting solution' as the cuprous chloride, separating they lsolution from the pre-- cipitate and returning the solution to the ore, applying calcium hydroxide tothe chloridetprecipitate, separating the resulting calcium chloride from the resulting co per4 oxide, and reldissolving'thecopper o-Xi e in an electrolyteiree from chlorine, and elec-v," trolyzng the resulting copper solution vto deposit .the copper as the electrolytic metall.`

28; A metallurgical process comprising treating ores otfcjopper with a solvent for the copper, precipitating ythecopper'from Q the-resulting' solution yas `the cuprous chloride, 'separating *the solution from" the,

A precipitate and .returning the'solution to theI ore,'applying calcium hydroxide to the. A chloride precipitate, separating i `ing calcium chloride from the resulting copper oxide, rie-dissolving' the copper ofXide in 'a sulphatey solution, and' electrolyzing the resulting` copper sulphate to obl tain the electrolytic metal and vregenerate the sulphate solvent.

24. A `metallurgical` processi"comprising;

treating ores of copper with a solvent for l. the copper, separatingthecopper solution from the ore, chemically precipitatingA the copper from the "solution,v se arating the precipitate from the resulting epleted copper solution, and then electrolyzing the so-` lution depleted of ,its copper and returning l the electrolyzed solution to the' ore.

25; A metallurgical process 4comprising treating ores of copper with a solvent for the4 resultf theA copper, separating the resulting copper solution from the; ore, chemically precipitating the copper from the solution, separating the resulting chemical precipitate from the resulting solution depleted in' copper, elec` trolyzing the solution depleted in copper and `returning' it to, the ore, yre-dissolving the lcopper of the precipitate with a solution Separate romrthe leach solution, and@- electrolyzing the resulting copper solution to obtain'the electrolytic metal.L 26. vA process comprising, .treatirng'` ores of copper with anz acid`solution to dissoli'f'e the copper from the oreprecipitating Lthe copper from the' 'resulting solution as the to a copper electrolyte containing salts of "iron' to'reduceferric `salts formed vbyIk electrolyzing theI .solution to the ferrous condip vtion, and then when the precipitate becomes impoverished in copper and containing'undesirable impurities' roasting the precipitate sulphide,-applyingthe sulphide precipitate A residue and applying the roasted precipitate residue tol the' electrolyte.

. 27; Ar process comprising, leaching copper ores to dissolye the copper, precipitating the copper from lthe `resulting 'solution `asthe sulphide, vreturning the 'resulting barren so? -lution tofthe ore, roasting ,the precipitata-3,` treating'the` roasted `precipitate with a solu.

tion separate from the leachsolution vto redissolve the copper, an'd'elect'rolytzing the resulting Qop'per solutiorrito -plotainthe electrolytic metal. t i

' 2,8; A process'comprising, leaching copper oreste dissolvethe copper, precipitating the copper froml the 'resulting fsolution with a chemical precipitant,l returning the resulting barren solution tothe ore, roasting thecopper precipitate, treating the roast'ed4 precipitate with a solventforlthe copper separate from the leach solution to redissolve the'copper, Iellectrolyzing the resulting cop- 1 per-solution Ito 'deposit tlie`copper as the 'electrolytic metal, and returning the electrolyzed'solution to the Toasted precipitate.

291 A lprocess ofJ producing electrolytic copperfrom its ores in Which `the leach solution 'is'maintained separate yfrom the electiolyte,I comprising,` leaching the ore with 'a' solventy for the copper, precipitating the copper from the resulting solution with a ico chemical precipitant, separating ,theprel cipitate from the solution, returning the barrgeeeneii lut-ion, re-dissolving the sulphide precipitate in a relativelyv rich copper solution containing salts of iron, electrolyzing the sollition to deposit copper and regenerate ferrie iron, returning'thel regenerated ferrie iron solution to the copper sulphide precipitate to re-dissolve more copper with the simultaneous reduction of the ferrie iron to the ferrous iron, and repeating the cycle indelinitely to convert the copper of the sulphide precipitate into the electrolytic metal.

'31. A process comprising precipitating copper from relatively lean or relatively foul solutions, separating' .the precipitate from the resulting solution, redissolvingaportion of tlie copper of the unroasted precipitate in a relatively rich copper solution containing salts of iron, electrolyzing the resulting solution to deposit copper and regenerate acicl and ferrie iron, returning the solution to the precipitate to rediseolve more copper with the 'simultaneous reduction of the ferrie iron tothe ferrous iron and continuing the cycle to convert the copper of the precipitate into tlie'electrolytic metal, roasting a portion of the precipitate to convert the copper into the oxide, and applying the roasted portion of the precipitate to the electrolyte.

WLLlAM E. GREENAVVALR 

